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396 or 454?

Discussion in 'Chevy Trucks' started by Buckett, Mar 29, 2005.

  1. Buckett

    Buckett Junior Member
    Messages: 1

    I have a 1984 Chevy 1 ton 4 door dually with a flat bed and when I bought it I was told it has a 396 but another guy told me he thinks its a 454 because it is an 84 model. Can anyone tell me how to tell the difference? Any help would be greatly appreciated!
  2. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    Look to see if it externaly balanced or not and look at the casting #'s

    Oh......and if its stock its a 454, coulda been swaped though
  3. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    The 396 was phased out after 1969, replaced with a 402 until 1972 (but still badged as a 396 on the car and a 400 on some trucks).

    At quick glance, the 366, 396, 427, and 454 all look alike, but there are subtle differences. All will swap in place of each other.

    As mentioned, the easiest way to tell a 454 is to look at the harmonic balancer on the front of the crankshaft. It is externally balanced, meaning the harmonic and flywheel are specific to the 454 and won't work on any other older Rat motor. Look for large cutouts in the side of the casting (not just drill marks, those are for fine balancing).

    If the motor is supposed to be original, it would be a 454.
  4. karl klein

    karl klein Senior Member
    Messages: 557

    i think the 454 has 7 bolt holes on each valve cover and a 400 has 4
  5. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    That would be a 400 small block, a totally different animal.

    The 396/402 has 7 just like a 454.

    As mentioned, some early 70's trucks used the 400 emblem to signify a 402 engine... stupid but thats what they did.
  6. PDQ Pete

    PDQ Pete Senior Member
    Messages: 139

    I think there is numbers on the engines right side front where the head meets the block there's a small pad with numbers punched in to it.
  7. Yaz

    Yaz PlowSite.com Addict
    from NH
    Messages: 1,061

    The numbers on the block are the only way to realy tell. Besides it could be a block of 396 borred after all these years with a 454 crank etc. if it could only talk! lol... Good thing you don't live closer, I would be knoking on your door begging you to sell it to me. I have been getting the bug to drop a 396 into my Camaro!
    Last edited: Apr 14, 2005